In the example of a vascular filter, the filter may be designed to resist movement from the desired site for treatment in a cranial direction, defined as being opposite a caudal direction. These types of filters are often resilient, and can be radially compressed into a smaller size, and may be removed by a catheter system that is inserted into the femoral artery, has a hook or loop member that passes through a passage or lumen through the catheter which catches the filter, and pulls the filter into the catheter lumen in the caudal direction. The catheter system and captured filter may then be removed from the patient.
It may also be desirable to remove a filter in the cranial direction, by introducing a catheter retrieval system through the jugular artery or brachial artery, and approaching the filter from the cranial direction. However, this approach may not be desirable, if the particular filter is designed to resist movement in the cranial direction.
The retrieval system of the present invention is capable of retrieving a filter when approaching from either direction. In other words, the present catheter-based retrieval system can be inserted through the femoral artery and approach the filter from the caudal direction to retrieve the filter, or through the jugular or brachial artery and approach the filter from the cranial direction, to retrieve the filter. This versatility is provided for approaching the filter from either direction, but enables the movement of the filter during retrieval to be in either direction. Accordingly, the filter can be pulled in the direction of movement that the filter does not resist, regardless of the direction from which the catheter-based retrieval system approaches the filter.
One example of a retrieval catheter system according to the present invention thus allows a filter to be designed to resist movement in the cranial direction, while still permitting retrieval by approaching the filter with a catheter-based retrieval system from either the cranial direction or the caudal direction.
In operation of a vascular filter retrieval system, the system may provide for “pulling” the filter a slight distance in the caudal direction to retract the filter anchors or barbs from engagement with the vessel, before “capturing” the filter within the catheter system, and then retrieving the catheter system and captured filter from whichever access point was selected, and thus in whichever direction is desired. This flexibility of approach may provide greater therapeutic options for treatment of patients.
Accordingly, a general possible object of the present invention is to provide filter retrieval systems for retrieving a previously implanted medical filter, and methods for using the retrieval systems.
Another possible object of this invention is to provide an improved filter retrieval system capable of retrieving a filter in either a proximal or a distal direction, as may be preferred by a physician.
These and other possible objects, features and advantages of the present invention will be apparent from and clearly understood through a consideration of the following detailed description of the preferred embodiment.
Many catheter systems are used with a flexible guidewire. The guidewire is often metal, and is slidably inserted along the desired body passage. The catheter system is then advanced over the guidewire by “back-loading” or inserting the proximal end of the guidewire into a distal guidewire port leading to a guidewire lumen defined by the catheter system. Such a guidewire lumen may extend along the entire length or only part of the catheter.
It is desirable to provide a balloon catheter having an optimum combination of various performance characteristics, which may be selected among: flexibility, lubricity, pushability, trackability, crossability, low profile, pull strength, inflation/deflation times, inflation pressures, and others. Flexibility may relate to bending stiffness of a medical device (balloon catheter and/or stent, for example) in a particular region or over its entire length, or may relate to the material hardness of the components. Lubricity may refer to reducing friction by using low-friction materials or coatings. Pushability may relate to the column strength of a device or system along a selected path. Trackability may refer to a capability of a device to successfully follow a desired path, for example without prolapse. Crossability may be clarified by understanding that physicians prefer to reach the desired site with the balloon catheter while encountering little or no friction or resistance. Profile may refer to a maximum lateral dimension of the balloon catheter, at any point along its length.
The balloon catheter of the present invention provides various advantages, which may include: pushability, optimized flexibility along the catheter length, torsional strength, pull strength, low profile, etc. Some embodiments of the present invention may also provide additional benefits, including smooth transitions in flexibility, lubricious guidewire lumen, etc.
Structurally, catheters may have a flexible shaft extending between a proximal end and a distal end, and define one or more tubular passages or “lumens” extending through part or all of the catheter shaft. Such lumens often have one or more openings, referred to as “ports.”
When a lumen is adapted to slidingly receive a guidewire, it is referred to as a “guidewire lumen,” and it will generally have a proximal and distal “guidewire port.” The distal guidewire port is often at or near the catheter shaft distal end.
A hub is often affixed to the catheter shaft proximal end. The hub may serve a variety of functions, including providing a handle for manipulating the catheter, and/or defining proximal port(s) communicating with lumen(s) defined by the catheter shaft. When the catheter has a guidewire lumen, a proximal guidewire port may be located at some point along the sidewall of the catheter shaft, or a hub may define the proximal guidewire port.
A guidewire has a flexible wire-like structure extending from a proximal end to a distal end. The guidewire will usually be of a size selected to fit into and slide within a corresponding guidewire lumen of a catheter.
The terms “tube” and “tubular” are used in their broadest sense, to encompass any structure arranged at a radial distance around a longitudinal axis. Accordingly, the terms “tube” and “tubular” include any structure that (i) is cylindrical or not, such as for example an elliptical or polygonal cross-section, or any other regular or irregular cross-section; (ii) has a different or changing cross-section along its length; (iii) is arranged around a straight, curving, bent or discontinuous longitudinal axis; (iv) has an imperforate surface, or a periodic or other perforate, irregular or gapped surface or cross-section; (v) is spaced uniformly or irregularly, including being spaced varying radial distances from the longitudinal axis; or (vi) has any desired combination of length or cross-sectional size.
Any suitable additional material may also be used to make catheters and hubs as described, including polymers and other materials suitable for use with medical devices.
It is of course possible to build various kinds and designs of catheters according to the present invention, by various techniques and of various materials, to obtain the desired features. It should be noted that the present invention also relates to methods for making and using medical devices, during or in preparation for medical treatment of a patient.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings. The invention will be explained in greater detail below with reference to the attached drawings of a number of examples of embodiments of the present invention.